docs: def __findout_decl_type(match_class, **keywds):
          """implementation details"""
          if 'decl_type' in keywds:
              return keywds['decl_type']
  
          matcher_args = keywds.copy()
          del matcher_args['function']
          del matcher_args['recursive']
          if 'allow_empty' in matcher_args:
              del matcher_args['allow_empty']
  
          decl_matcher = match_class(**matcher_args)
          if decl_matcher.decl_type:
              return decl_matcher.decl_type
          return None